Print head and platen printer device

ABSTRACT

A novel print head and platen configuration for a high speed printer is disclosed wherein the print head is a hollow cylindrical shape fabricated from a material which is measurably softer than the material used in the platen assembly. The print head is easily removable from its supporting structure. The hard platen has an appreciably long life and together with the print head assembly markedly improves on the print definition of the underlying printed copies.

United States Patent 11 1 Wang [ Oct. 30, 1973 PRINT HEAD AND PLATEN PRINTER DEVICE Cheng-IIua Wang, Newton, Mass.

[52] U.S. Cl 197/18, 197/48, 197/55, 101/368 [51] Int. Cl B4lj 23/04 [58] Field of Search 197/144, 55, 52, 197/18, 48; 101/368, 375

[56] References Cited UNITED STATES PATENTS 3,071,071 1/1963 Beaver 101/380 3,109,368 11/1963 Luttrell 101/376 3,247,941 4/1966 Beattie et a1. 197/55 3,425,347 2/1969 Nard 101/376 2,895,584 7/1959 l-lickerson et a1... 197/52 1,149,855 8/1915 Pierce 197/144 1,451,423 4/1923 Handley 197/144 1,424,905 8/1922 Hess 197/144 1,534,116 4/1925 Hess... 197/144 2,389,499 1111945 Gordon 197/144 2,341,481 2/1944 Smith 197/144 X 1,555,104 9/1925 Corcoran. 197/144 3,418,933 12/1968 Schaefer..... 197/144 X 3,289,574 12/1966 Webb 197/55 X 1,382,417 6/1921 Edmundson 197/144 Primary Examiner-Edgar S. Burr Attorney-Fred Jacob and Ronald T. Reiling [57] ABSTRACT an appreciably long life and together with the print head assembly markedly improves on the print definition of the underlying printed copies.

v 6 Claims, 2 Drawing Figures PATENTEBucr 30 ms INVENTOR Cheng- Hua Wang iuitilliiit.

Attorney SUMMARY OF THE INVENTION This invention relates to improvements in printer apparatus and more particularly to a novel character drum and platen configuration for a high speed serial printer.

Heretofore printers employing a striking print head on a platen surface have utilized a hard print head surface and a relatively soft platen surface. The print head surface was usually constructed of either a hard plastic or a metallic material whereas the platen was constructed of a relatively softer substance such as rubber. The platen would under repeated striking wear unevenly and harden in particular areas resulting in uneven print especially in the underlying copies. This would necessitate a replacement of the worn platen drum surface. Even with a new platen surface, the distinctness and clarity of written characters on the underlying copies would significantly diminish as the number of copies increased. This phenomena of progressively less sharp and distinct characters as well as platen deterioration is correctable by practicing the present invention.

Briefly, the present invention provides for a relatively soft and easily replacable print head in combination with a hard platen. The print head includes a cylindrical character drum fabricated from a soft but durable material. The relatively soft print head transmits sufficient print energy to effectuateprinted copies up to six part forms while maintaining the surface integrity of the first or original copy. The platen is made of an appreciably hard material which acts as an extremely stiff backing against the copies of print medium adjacent to it. This allows for significantly greater absorption of printing energy in these underlying copies than would otherwise be obtainable by using a conventional platen. Furthermore, the hard platen is also lesssusceptible to damage or disfigurement due to repeated striking by the print head.

An object of this invention is to provide a printer wherein there is no appreciable wear factor associated with the platen.

Another object of this invention is to provide a printer with a new and improved platen that is appreciably harder than previous conventional platens.

Yet another object of this invention is to provide a printing environment whereby the underlying copies of print medium absorb a significant proportion of the print energy and hence render a better print definition than heretofore obtainable.

A still further object is to provide a printer with a new and improved print head that is relatively softer than the platen.

The above, as well as other features of the present invention, may be more clearly understood by reference to the following detailed description when considered with the drawings.

BRIEF DESCRIPTION OF TI-IE'DRAWINGS FIG. 1 is an overall perspective view of a rotatable, displaceable print head and platen assembly; and

FIG. 2 is a cross-sectional view of the print head and associated supporting means.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more specifically to the drawings, in FIG. 1, there is shown a printer having a print head similar in operation to that disclosed in US. Pat. No. 3,247,941 to H. S. Beattie et al. The print head 10 is simultaneously displaced along and rotated about the axis 12 so as to thereby increment a given character to a given print position. For simplicity, the print head is merely shown as being pivotable about a second axis 14. An exact implementation of the various motions is readily apparent from the above mentioned US. Pat. No. 3,247,941. The print head is further depicted as being in operative position relative to the platen l6 and associated roller 18. The platen 16 and associated roller 18 are rotatable about the axes 20 and 22 respectively. Disposed between the platen l6 and roller 18 there is shown a six part fold of printing medium comprised of a first copy 24 and a number of underlying carbon copies 2834. A typical ink transfer medium 36 is disposed between the first copy 24 and the print head 10. The above described printer is merely representative of a rather commonly known type of single element matrix printer. A further reference disclosing a similar printing device is shown in US Pat. No. 3,302,765 to Hickerson et al.

The print head 10 of FIG. 1 is further shown in FIG. 2 to be comprised of the molded hollow cylindrical shaped character drum 38 with the inner supporting sleeve 40 closed at one end and suitably connected to the carriage rod 46. The drum 38 is preferably made of urethane with a Durometer A hardness in the range of to 85. This cast urethane shape with the aforementioned hardness is available from the Globe Rubber Company of Quincy, Mass. A typical drum contains 96 characters and measures 2% inches in length with an outside diameter of 0.572 inches and a thickness of 1/32 of an inch. The inner supporting sleeve 40 can be fabricated from any of the lightweight metals such as, for example, aluminum.

Drum 38 is oriented in a predetermined manner with respect to the keyhole cavity 42 of support sleeve 40 and secured thereto by any of a number of epoxies suitable for adhering synthetic rubber to a metal surface. The character drum 38 is further positionably fixed relative to carriage rod 46 by engagement of the keyhole cavity 42 with the associated key rise on mount 44. The entire print head 10 is secured to the carriage rod 46 by the nut 48.

As previously stated, one object of the present invention is to describe a printing environment whereby the underlying copies 28 through 34, and especially the latter three 30-34, absorb a significant portion of the energy imparted from the printing stroke of print head 10. This is achieved in the present invention by constructing the platen 16 of a hard material that characteristically reflects the imparted energy without appreciably absorbing any. The underlying copies 30,32 and 34 thereby gain a proportionate amount of energy which would otherwise have been dissipated in a soft conventional platen. This energy gain results in a sharper and more precise character definition in the underlying copies.

The additional ingredient of providing a soft print head 10 allows for some energy absorption at the point where it may be necessary, namely, at the first copy. In

order to prevent any penetration or disfigurement of the first copy surface, the previously described urethane drum 38 is used in combination with the hard platen. This drum provides the degree of impact energy absorption needed to prevent disfigurement of the first copy 24.

A plastic platen with a measured hardness of 90D (Durometer measurement) when used in conjunction with the print head renders the desired markedly improved character distinctness in the underlying copies. This is in contrast to the conventional print head and softer platen configuration wherein the platen is constructed of hard rubber measuring 90A in hardness. Printing tests have been run on 6 part folds of copy for the purpose of comparing the two systems. Results showed a marked improvement in the character distinctness obtained from the 90D plastic platen configuration.

Metal platens significantly harder than the aforementioned plastic platen have also been tested with similar occurring results. When resorting to metal, the additional dynamic influence of a heavy inertial mass in a high speed print system must also be considered. This dictates going to lightweight metals such as aluminum. Aluminum platens demonstrate both a desired lightness in weight as well as a significantly hard and stiff backing surface for the many folds of print medium.

The urethane character drum 38 has proven to be extremely durable over a lengthy period of being repetitively struck against a hard metal platen surface. Drums have been tested at a printing rate of 30 strokes per second using an energy level equivalent to that required for printing six copies. This was done without the benefit of any print copy disposed between the drum and the hard metal platen. It was found that even in the worst possible case of repetitively striking a small character (such as a comma or period), that the drum 38 had a printing life of over 1,200 hours.

The above testing also indicated a marked durability in the hard platens which were used in the tests. In each case, the harder platen surface was not disfigured after the aforementioned repetitious striking by the drum.

One additional consideration must be considered in implementing the soft character drum and hard platen configuration. This involves the rather smooth metal platen failing to adequately engage the copy for advancement of the paper. This slippage is remedied by coating the periphery of the metal platen with a thin layer of material 50 with the necessary frictional surface for engaging and advancing the paper. A 4 to 10 mil layer of urethane of only 95A Durometer hardness produces the desired frictional surface on the platen. This thin layer of frictional material will not significantly affect the overall platen hardness and moreover will not act as an appreciable absorbant of the printing energy. This last requisite of the frictional layer dictates the choice and thickness of the material layer for the platen surface. It is to be emphasized that in an ordinary serial printer'wherein the paper fold is advanced by sprocketed hole engagement that this additional step of providing a layer of frictional material over the platen surface would not be necessary.

While specific embodiments of the platen and character drum have been shown, it will be understood that various modifications and additions can be made to the disclosed configuration without departing from the novel concepts and spirit of this invention which are limited only by the following claims.

I claim:

1. Printer apparatus comprising:

a platen body having an endless surface, said body being rotatable about a first axis, and

a print head having an endless surface, said head being rotatable about and moveable along a second axis so as to position a character for printing, said print head comprising:

a cast shell consisting of a material which is measurably softer than the material from which said platen body is formed, said material of said cast shell having a hardness entirely within the Durometer A hardness range of to 85, said cast shell furthermore having integrally formed surface characters, and

an inner support for mounting said cast shell thereon, said inner support comprising a metal sleeve which is affixed to the interior surface of said cast shell. I

2. The apparatus of claim 1 wherein said material of said cast shell is urethane.

3. The apparatus of claim 2 wherein the platen material has a composite hardness greater than or equal to a Durometer hardness of D.

4. Printer apparatus comprising:

an impacting means comprising a cast shell with raised characters formed integrally on the exterior surface thereof, said cast shell consisting of a material having a hardness entirely within the Durometer A hardness range of 75 to 85, and an inner sup port mount for mounting said cast shell thereon, said inner support mount comprising a metal sleeve which is affixed to the interior surface of said cast shell;

a print medium disposed in spaced relation with said impacting means; and

a backup means, located on the opposite side of said print medium from said impacting means, said backup means consisting of a material having a measurable Durometer hardness greater than the hardness of said cast shell.

5. The apparatus of claim 4 wherein said material of said cast shell is urethane.

6. The apparatus of claim 5 wherein said back up mean has a surface hardness greater than or equal to a Durometer hardness of 90D. 

1. Printer apparatus comprising: a platen body having an endless surface, said body being rotatable about a first axis, and a print head having an endless surface, said head being rotatable about and moveable along a second axis so as to position a character for printing, said print head comprising: a cast shell consisting of a material which is measurably softer than the material from which said platen body is formed, said material of said cast shell having a hardness entIrely within the Durometer A hardness range of 75 to 85, said cast shell furthermore having integrally formed surface characters, and an inner support for mounting said cast shell thereon, said inner support comprising a metal sleeve which is affixed to the interior surface of said cast shell.
 2. The apparatus of claim 1 wherein said material of said cast shell is urethane.
 3. The apparatus of claim 2 wherein the platen material has a composite hardness greater than or equal to a Durometer hardness of 90D.
 4. Printer apparatus comprising: an impacting means comprising a cast shell with raised characters formed integrally on the exterior surface thereof, said cast shell consisting of a material having a hardness entirely within the Durometer A hardness range of 75 to 85, and an inner support mount for mounting said cast shell thereon, said inner support mount comprising a metal sleeve which is affixed to the interior surface of said cast shell; a print medium disposed in spaced relation with said impacting means; and a backup means, located on the opposite side of said print medium from said impacting means, said backup means consisting of a material having a measurable Durometer hardness greater than the hardness of said cast shell.
 5. The apparatus of claim 4 wherein said material of said cast shell is urethane.
 6. The apparatus of claim 5 wherein said back up mean has a surface hardness greater than or equal to a Durometer hardness of 90D. 